Generally, patient positioning systems are used to support and position patients during diagnostic or therapeutic medical procedures. Conventional patient positioning systems typically comprise a table assembly and a drive assembly coupled to the table assembly and configured to position a patient supported by the table assembly.
The table assembly includes a patient support table, on which the patient undergoing the medical procedure lies. Typically, the drive assembly configured for driving the table assembly includes actuator assemblies for effecting longitudinal, lateral and/or vertical movement of the patient support table for enabling convenient positioning of the patient.
The drive assembly can include a linear-type drive assembly, for example, a rack and pinion drive assembly comprising a motion-inducing member, a pinion coupled to the motion-inducing member, and a rack movably coupled to the pinion. The motion-inducing member can comprise one of a manually operable configuration or a drive motor with a drive shaft coupled directly to the pinion to drive the pinion. The rack is then driven by the motion-inducing member via the pinion.
One limitation associated with the rack and pinion drive assembly is the possibility of an uncontrolled motion of the rack resulting from a single point failure of the pinion. The uncontrolled motion of the rack may result in a patient fall during longitudinal and/or lateral movement of the patient support table. In a tilted condition of the patient support table, when one of the pinion or the drive shaft connecting the motion-inducing member to the pinion gets cut, the rack may move down due to gravity along with the patient and collide with the surrounding environment causing injury to the patient or medical staff operating the patient positioning system and/or may cause damage to the patient support table or other equipment proximate to the patient support table.
Some existing patient positioning systems employ a safety device comprising a fail-safe brake. However, such brakes may not be able to control the motion of the patient support table resulting from the failure of the rack and pinion drive assembly. Moreover, the presence of a redundant second fail-safe brake in a parallel axis reduces a longitudinal stroke required for carrying out the medical procedures. Thus, the overall size of the drive assembly increases thereby increasing the system complexity.
Further, various other prior art safety devices do not address the single point failure of the pinion in the rack and pinion drive assembly. Addressing the single point failure of the pinion in the rack and pinion drive assembly may enhance patient safety. Hence there exists a need for a compact drive assembly providing an enhanced patient safety while maintaining the longitudinal stroke available for the medical procedure.
Some patient positioning systems also provide for vertical patient movement. A drive assembly for effecting a vertical movement of the patient positioning system, for example, a gear train drive assembly comprises a motion-inducing member coupled to a gear train by a gearbox. The motion-inducing member includes a drive motor that drives the gear train to enable a telescopic lift mechanism in the patient positioning system.
Further, the gear train drive assembly may comprise a ball screw comprising multiple stages driven by the gear train. The gear train comprises multiple gears and each stage of the ball screw is driven through a corresponding gear. One limitation associated with the gear train drive assembly is the possibility of a gear detachment. Upon encountering the gear detachment, the gear train drive assembly may collapse thereby initiating a downfall of the patient support table along the vertical axis.
The downfall of the patient support table may result in injuries to one or more of the patient and/or the medical staff operating the patient positioning system. Further, the downfall of the patient support table may cause damage to the surrounding environment including systems positioned at close proximity to the patient positioning system.
Known safety devices for patient positioning systems, providing for vertical patient movement comprise a non-reversible gearbox and a fail-safe brake. However, such safety devices may not be able to prevent the downfall of the patient support table in case of gear detachment.
On the other hand, as in one of the solutions provided in the art, adding a fail-safe brake on each stage of the ball screw may increase the minimum height of the table assembly. The increment in the minimum height of the table assembly may pose difficulties in loading or unloading the patient on the patient support table.
Hence, there exists a need to provide a mechanism to prevent the collapsing of the gear train drive assembly in case of a gear detachment, while maintaining the minimum table height associated with easy patient loading or unloading.
All in all, there exists a need to provide a patient positioning system comprising a simpler, compact and robust mechanism for displacing the table assembly longitudinally, laterally and/or vertically while providing an easy access and increased safety to the patient and operator facility thereby enhancing reliability and cost savings.